Continuous casting die with compatible lining and jacket

ABSTRACT

A continuous casting die, particularly for copper base melts, has a graphite lining and a copper jacket, which are connected by molybdenum fasteners. The thermal expansion coefficients and the other physical characteristices are such that threaded joints between the fasteners and the jacket do not loosen in service and bearing pressure between the lining and the jacket is maintained.

-. [111 3,809,148 May 7, 1974 United States Patent t [191 Pulsifer CONTINUOUS CASTING DIE WITH 3,580,328 I -Eppich............................

Primary Examiner-R. Spencer Annear 'Attorney, Agent, or Firm-Morse, Altman, Oates &

Bello COMPATIBLE LINING AND JACKET [75] Inventor: Verne Pulsifer, Pittsburg, Pa. [73] Assignee: Copper Range Company, White Pine, Mich.

[221 Filed: Nov. 30, 1972 [21] Appl. N0.: 310,688

[57] ABSTRACT A continuous casting die, particularly for copper base melts, has a graphite lining and acopper jacket, which US. 164/283 M, 164/138, 249/134 Int Cl B22! 11/00 are connected by molybdenum fasteners. The thermal expansion coefficients and the other physical characteristices are such that threaded joints between the fasteners and the jacket do not loosen in service and jacket is bearing pressure between the lining and the maintained.

UNITED STATES PATENTS l l/ 1966 3,237,773 Woodburn, 164/82 x 9 Claims, 3' Drawing Figures R E DIE Dis 0A CB U E M COPPER BASE SHEET CONTINUOUS CASTING DIE WITH COMPATIBLE LINING AND JACKET DETAILED DESCRIPTION The present invention relates to metallurgical apparatus and, more particularly, to continuous casting die of the type in which a continuous flow of melt produces a continuous length of stock.

Difficulties have been encounteredin the use of dies for continuous casting of such metals as copper and copper alloys. Typically, a continuous castingdie comprises a refractory lining, for example composed of graphite, and a heat conducting jacket, for example composed of copper. When the cast section is of a highly symmetrical configuration, for example circular or hexagonal, the contact between the jacket and the lining can be made quite intimate by press fitting in order to ensure a low thermal resistance joint between the jacket and the lining. When the cast section is unsymmetrical, it is much more difficult to obtain a low resistance joint between the jacket and the lining. This' change of length divided by original length. If the bolt,

however, changes length relative to the graphite by as much as 0.001 inch, there may appear a gap between the graphite and the copper by as much as 0.001 inch.

This small gap represents a very large loss in heat transfer to the cooling jacket.

The primary object of the present invention is to provide a continuous casting die, particularly for copper base melts, which has graphite lining members, copper (or other high thermal conductivity metal) jacket members, and molybdenum fastener members, which are locked to thecopper jacket members and bear against the graphite lining members. Molybdenum and graphite, particularly fine grain graphite, have closely alike thermal coefficients of expansion throughout the service temperature range of continuous die casting equipment for copper base melts. In operation, the roughly uniform expansion of the lining and fastener members, together with the tension generated in the jacket and fastener members by the clamping force applied across the graphite members, efficaciously precludes loosening of members during protracted contin-- uous casting.

Other objects of the present invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the apparatus,

disclosed herein as embodyingthe present invention,

. the scope of which will be indicated in the appended claims.

I BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary perspective view of a preferred continuous casting die embodying the present invention; I

FIG. .2 is an enlarged fragmentary cross sectional view of a portion of the die of FIG. 1; and

FIG. 3 is a graph illustrating certain principles of the present invention;

DETAILED DESCRIPTION Generally, the embodiment of the present invention shown in FIG. 1 is a die for continuously casting copper sheet 8 from a melt 9. This die comprises a pair of parallel, inner graphite lining'plates 10, 10 and a pairof side dams 11, llbetween plates 10, I0 and along their longitudinal edges. Side dams 11, 11, which are strips of rectangular cross section, and plates 10, 10 define a die cavity 14 into which melt 9 is flowed, within which melt 9 solidifies and from which resulting sheet 8 advances. In intimate contact with the outer faces of lining plates 10, 10 are the inner faces of a pair of jacket plates 16, 16. And at theouter faces of lining plates 10, 10 are backing plates 18, 18, which are shouldered as at 20,20 to provide channels 22, 22. Within channels 22, 22, a coolant, such as de-ionized water, flows between the jacket and backing plates. Preferably, lining plates 10,10- and side dams .11, 11 are composed of graphite and jacket plates 16, 16 are composed of a high thermal conductivity metal such as copper. For best results, the graphite has a fine grain characterized by grains of less than 0.01 .inch in average diameter. Typically, backing plates 18, 18 are composed of stainless steel, bronze or chrome plated mild steel.

As shown in FIG. 2, the outer surface of 23 of graphite liner plate 10 is in intimate contact with the inner surface 24 of copper jacket plate 12, the two surfaces being held together under pressure by molybdenum fasteners, two of which at shown at 26, 28. Fastener 26 is in the formof'a screw having a threaded shank 30, the outer extremity of which is turned into a mated threaded bore 32in jacket plate 16. Shank 30 extends through a bore 34 in graphite liner plate, the bore being slightly larger in diameter than the shank. Fastener 26 has a head 36 with an inner face 38 that is flush with the inner face of graphite liner plate 10 and an outer bearing surface 40 that is seated against a shouldered seat 42 in graphite liner plate 10. Seat 42is larger in diameter than head 36. The arrangement is such-that head 36 clampsgraphite liner plate 10 against copper jacket plate 16 while permitting slip between the grahite liner plate and the copper jacket plate duringser vice. The dimensionalstability and. surface microstructure of the molybdenum screw and the copper bore are such that differences in volumeresultingfrom thermal expansion in the vicinity of the mated portions of the screw and bore threadings are negligible in comparison with the grippingforces involved betweenthemeshed configurations. In other wordsthe threadedborein the copper jacket plate will continue to grip a snug screw fastener on heating, the differences in the relative diameters of the bore and the thread on thermal cycling not being significant.

Fastener 28 consists of aclamp 44 and a screw 46. Clamp 44 includes a body portion 49 and an arm portion 50, body portion 49 havinga flat outer'face 52 that abutsagainst the face-of jacket plate 16 and portion 50 having anouter face 54 that abuts against a shouldered face 56 atthe edge of graphite liner plate 10. Laterally there is sufficient clearance between the liner plate 10 and jacket plate 12. Projecting through a bore in the body portion of clamp 49 is the threaded shank of screw 46, which is turned into a mated threaded bore 58 in jacket 12. Sufficient clearance between the shank and the bore through body portion 49 is provided to enable free rotation of the shank therein. The head 60 of screw 46 is tapered at 48 to bear against the corresponding tapered surface of the bore in body portion 49. Here again the arrangement is such that tight contact is maintained between graphite liner plate 10 and copper jacket plate 16 by clamp 28, notwithstanding the ability of the graphite liner platev to slip with respect to the copper jacket when in service.

- EXAMPLES In one example, lining plates- 10, 10 are 20 inches wide and 1 inch thick, side dams 11, 11 are inches wide and 1 inch thick, and jacket plates l6, 16 are 20 inches wide and 1 inch thick. The lining plates and side dams are composed of fine grain graphite characterized by grains having an average diameter of about 0.006 inch. The jacket plates are composed of high conductivity copper. The fasteners are composed of commercial molybdenum, i.e. 99% pure. The thermal conductivity of the graphite and copper liners is in excess of 68 BTU feet/hr/fr /T. In an alternative example, the fasteners are composed of an alloy 90% molybdenum an tungsten. Ordinarily the service temperature of the mold ranges from room temperature to 1,200F.

The advantageous results achieved by the relationships among the various components above discussed are thought to be at least in part the result of an additional effect that is not apparent superficially. This effect is bending as a result of differential expansion between the graphite and the copper that does not result in slip. Bolting too tightly tends to improve heat transfer and increase the bending effect by virtue of the thermal gradients involved. Just the right clamping force results in an optimum resultant cooling efiect. This force, as measured by means of a torque wrench, has been found to be in the range of 10-inch pound and IOO-inch pounds, as tested by opposed pressure surface of 0.1 square inch each.

FIG. 3 illustrates thermal expansion relationship between molybdenum and graphite. The thermal expansion coefficient of graphite throughout the service temperature range is as follows:

Temperature (F) Coefficient of Thermal Expansion The thermal coefficient of molybdenum throughout the service temperature range is as follows:

Temperature (F) Coefficient ofThermal Expansion 400 2.75 X 10" 800 2.75 X lo" As seen in FIG. 3, there is a substantially linear relationship between the thermal expansion coefficient of graphite and the thermal expansion coefficient of molybdenum.

' The present invention thus provides a novel continuous casting die, in which intimate thermal conduction is maintained between the die lining and the die jacket throughout wide range of service temperatures. Since certain changes may be made in the present invention without departing from the scope of the disclosure it is intended that all matter contained in the above description or shown in the accompanying drawings be interpreted in an illustrative and not in a limiting sense.

What'is claimed is:

1. A mold for continuously casting metal, said mold comprising lining means defining a mold cavity having a melt entrance and a casting exit, jacket means. intimately engaging said lining means, and fastening means mechanically connected to said jacket means and bear ing against said lining means, said lining means being composed of graphite, said jacket means being composed of a highly thermally conducting metal, said fastening means being composed of a molybdenum base metal.

2. The mold of claim 1 wherein said molybdenum base metal contains at least 95 percent molybdenum by total weight.

3. The mold of claim 1 wherein said jacket means is composed of a copper base metal.

4. A mold for continuously casting copper base metal, said mold comprising, in sequence from interior to exterior, lining means defining a mold cavity having a melt entrance and a casting exit, jacket means intimately engaging said lining means, fastening means mechanically connected to said jacket means and bearing against said lining means, and backing means in contact with said jacket means defining therewith conduit means for liquid coolant, said lining means being coma pair of lining strips and a pair of lining plates, said lining strips intimately contacting longitudinal face edges of said lining plates, a pair of jacket plates, inner faces of said jacket plates intimately contacting outer faces of said lining plates, and a plurality of fasteners fixed to said jacket plates and bearing against said lining plates, said fasteners being composed of a molybdenum base metal containing at least percent molybdenum by total weight, said lining plates and said fasteners having approximately the same coefficient of thermal expan sion.

6. The mold of claim 5 wherein at least one of said fasteners includes a screw having a threaded shank and a head, at least one of said jacket plates having a threaded bore and at least one of said lining plates having a guide bore aligned with said threaded bore, said head bearing against said lining plate, said threaded shank being turned into said threaded bore, said guide body portion, said guide bore being aligned with said threaded bore, said threaded shank being turned into said threaded bore, said body portion being sufficiently clear of said lining plate to permit relative movement between said jacket plate and said lining plate. 7

9. The mold of claim 8 wherein said graphite is characterized by fine grains generally less than 0.01 inch in diameter.

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2. The mold of claim 1 wherein said molybdenum base metal contains at least 95 percent molybdenum by total weight.
 3. The mold of claim 1 wherein said jacket means is composed of a copper base metal.
 4. A mold for continuously casting copper base metal, said mold comprising, in sequence from interior to exterior, lining means defining a mold cavity having a melt entrance and a casting exit, jacket means intimately engaging said lining means, fastening means mechanically connected to said jacket means and bearing against said lining means, and backing means in contact with said jacket means defining therewith conduit means for liquid coolant, said lining means being composed of graphite, said jacket means being composed of a copper base metal, said fastening means being composed of a molybdenum base metal containing at least 85 percent molybdenum by total weight, said coolant being water.
 5. A mold for continuously casting copper sheet, said mold comprising, in sequence from interior to exterior, a pair of lining strips and a pair of lining plates, said lining strips intimately contacting longitudinal face edges of said lining plates, a pair of jacket plates, inner faces of said jacket plates intimately contacting outer faces of said lining plates, and a plurality of fasteners fixed to said jacket plates and bearing against said lining plates, said fasteners being composed of a molybdenum base metal containing at least 85 percent molybdenum by total weight, said lining plates and said fasteners having approximately the same coefficient of thermal expansion.
 6. The mold of claim 5 wherein at least one of said fasteners includes a screw having a threaded shank and a head, at least one of said jacket plates having a threaded bore and at least one of said lining plates having a guide bore aligned with said threaded bore, said head bearing against said lining plate, said threaded shank being turned into said threaded bore, said guide bore receiving said shank with sufficient clearance to permit relative movement between said jacket plate and said lining plate.
 7. The mold of claim 6 wherein said graphite is characterized by fine grain generally less than 0.01 inch in diameter.
 8. The mold of claim 5 wherein at least one of said fasteners includes a clamp and a screw, said clamp having a body portion and an arm portion, said arm portion having a guide bore, at least one of said jacket plates having a threaded bore, said arm portion bearing against said lining plate, said body portion bearing against said jacket plate, said head bearing against said body portion, said guide bore being aligned with said threaded bore, said threaded shank being turned into said threaded bore, said body portion being sufficiently clear of said lining plate to permit relative movement between said jacket plate and said lining plate.
 9. The mold of claim 8 wherein said graphite is characterized by fine grains generally less than 0.01 inch in diameter. 